// Copyright 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_INPUT_PAGE_SCALE_ANIMATION_H_
#define CC_INPUT_PAGE_SCALE_ANIMATION_H_

#include <memory>

#include "base/macros.h"
#include "base/time/time.h"
#include "cc/base/cc_export.h"
#include "ui/gfx/geometry/cubic_bezier.h"
#include "ui/gfx/geometry/size_f.h"
#include "ui/gfx/geometry/vector2d.h"
#include "ui/gfx/geometry/vector2d_f.h"

namespace cc {

// Used in the CC to pass around a scale animation that hasn't yet been
// initialized.
struct PendingPageScaleAnimation {
    PendingPageScaleAnimation(
        const gfx::Vector2d _target_offset,
        bool _use_anchor,
        float _scale,
        const base::TimeDelta& _duration)
        : target_offset(_target_offset)
        , use_anchor(_use_anchor)
        , scale(_scale)
        , duration(_duration)
    {
    }
    gfx::Vector2d target_offset;
    bool use_anchor;
    float scale;
    base::TimeDelta duration;
};

// A small helper class that does the math for zoom animations, primarily for
// double-tap zoom. Initialize it with starting and ending scroll/page scale
// positions and an animation length time, then call ...AtTime() at every frame
// to obtain the current interpolated position. The supplied timing function
// is used to ease the animation.
//
// All sizes and vectors in this class's public methods are in the root scroll
// layer's coordinate space.
class CC_EXPORT PageScaleAnimation {
public:
    // Construct with the state at the beginning of the animation.
    static std::unique_ptr<PageScaleAnimation> Create(
        const gfx::Vector2dF& start_scroll_offset,
        float start_page_scale_factor,
        const gfx::SizeF& viewport_size,
        const gfx::SizeF& root_layer_size);

    ~PageScaleAnimation();

    // The following methods initialize the animation. Call one of them
    // immediately after construction to set the final scroll and page scale.

    // Zoom while explicitly specifying the top-left scroll position.
    void ZoomTo(const gfx::Vector2dF& target_scroll_offset,
        float target_page_scale_factor,
        double duration);

    // Zoom based on a specified anchor. The animator will attempt to keep it
    // at the same position on the physical display throughout the animation,
    // unless the edges of the root layer are hit. The anchor is specified
    // as an offset from the content layer.
    void ZoomWithAnchor(const gfx::Vector2dF& anchor,
        float target_page_scale_factor,
        double duration);

    // These should be called before the first frame of animation to initialize
    // the start time. StartAnimation should only be called once after creation.
    bool IsAnimationStarted() const;
    void StartAnimation(base::TimeTicks time);

    // Call these functions while the animation is in progress to output the
    // current state.
    gfx::Vector2dF ScrollOffsetAtTime(base::TimeTicks time) const;
    float PageScaleFactorAtTime(base::TimeTicks time) const;
    bool IsAnimationCompleteAtTime(base::TimeTicks time) const;

    // The following methods return state which is invariant throughout the
    // course of the animation.
    base::TimeTicks start_time() const { return start_time_; }
    base::TimeDelta duration() const { return duration_; }
    base::TimeTicks end_time() const { return start_time_ + duration_; }
    gfx::Vector2dF target_scroll_offset() const { return target_scroll_offset_; }
    float target_page_scale_factor() const { return target_page_scale_factor_; }

protected:
    PageScaleAnimation(const gfx::Vector2dF& start_scroll_offset,
        float start_page_scale_factor,
        const gfx::SizeF& viewport_size,
        const gfx::SizeF& root_layer_size);

private:
    void ClampTargetScrollOffset();
    void InferTargetScrollOffsetFromStartAnchor();
    void InferTargetAnchorFromScrollOffsets();

    gfx::SizeF StartViewportSize() const;
    gfx::SizeF TargetViewportSize() const;
    float InterpAtTime(base::TimeTicks time) const;
    gfx::SizeF ViewportSizeAt(float interp) const;
    gfx::Vector2dF ScrollOffsetAt(float interp) const;
    gfx::Vector2dF AnchorAt(float interp) const;
    gfx::Vector2dF ViewportRelativeAnchorAt(float interp) const;
    float PageScaleFactorAt(float interp) const;

    float start_page_scale_factor_;
    float target_page_scale_factor_;
    gfx::Vector2dF start_scroll_offset_;
    gfx::Vector2dF target_scroll_offset_;

    gfx::Vector2dF start_anchor_;
    gfx::Vector2dF target_anchor_;

    gfx::SizeF viewport_size_;
    gfx::SizeF root_layer_size_;

    base::TimeTicks start_time_;
    base::TimeDelta duration_;

    const gfx::CubicBezier timing_function_;

    DISALLOW_COPY_AND_ASSIGN(PageScaleAnimation);
};

} // namespace cc

#endif // CC_INPUT_PAGE_SCALE_ANIMATION_H_
